This invention relates generally to a power device with a lubricant anti-wicking facility and particularly to a power tool with facility for precluding wicking of lubricants and other forms of flowable substances from one compartment of a housing of the tool undesirably into and about the exterior of another compartment of the housing.
In some types of hand-held power tools such as, for example, drills, grinders, jig saws and the like, a plastic housing provides support for a motor in one compartment, referred to as a motor case, and gears in an adjacent compartment, referred to as a gear case. Typically, the housing is composed of two mating shell-like elements referred to as clamshell sections. Each clamshell section has an open side and is formed with a maze of inner walls which extend to the open side of the clamshell section. The walls separate the inner area of the clamshell section into the compartments which form the motor and gear cases. Further, each clamshell section and related walls are formed with peripheral edges or rims which are located in a common plane at the open side of the clamshell section.
During assembly of the various components of the power tool, the motor, gears and other components of the tool are assembled in respective compartments of one of the clamshell sections and interconnected for ultimate operation. In addition, the gears and bearings can be lubricated easily while exposed in assembly with the one clamshell section.
The mating clamshell section is then assembled with the clamshell section which contains the motor and the gears in such a manner that the peripheral edges of the clamshell sections are placed in facing engagement to form the housing of the tool. In addition, the peripheral edges of the walls of the mating clamshell sections are also placed into facing engagement to form enclosed compartments within the housing. The enclosed compartments then form the motor and gear cases. Fasteners, such as screw fasteners, are used to retain the clamshell sections in the assembled relation.
To preclude lateral movement of one of the assembled clamshell sections relative to the other, the peripheral edge of one of the clamshell sections is formed with an outwardly projecting rib while the peripheral edges of the other clamshell section is formed with an accommodating groove. When the clamshell sections are assembled, the rib is inserted into and nested in the groove to provide an interlock between the clamshell sections and thereby preclude relative lateral movement of the clamshell sections before and after the fasteners have been applied.
During use of the tool, the lubricant in the gear case is worked by the moving gears and is deposited on the inner walls of the gear casing. Subsequently, the lubricant deposits undesirably into the portion of the interlock which is contiguous with the gear case and begins to creep, by wicking or capillary action, to other portions of the interlock which are contiguous with the adjacent motor casing. Eventually, the creeping lubricant, which collects dirt and dust particles from inside and outside the housing, flows from the interlock onto the outside of the housing in the vicinity of the motor case and creates handling difficulties for an operator who normally holds this area when the tool is being used. In addition the creeping lubricant is drawn into the motor case by the flow of cooling air about the motor and contaminates the motor which affects the safe and efficient operation of the motor and causes a deterioration of motor parts.
The lubricant wicking problem is common where gears requiring lubrication are placed, by necessity, close to the motor and where the common housing for the gears and motor is formed with structure which accommodates creepage of the lubricant. Traditionally, attempts to solve this problem have included a variety of techniques such as the use of interference fits and rubber seals as well as the application of various sealing compounds.
While the foregoing techniques for reducing leakage of lubricants from a gear case are effective, they all require considerable additional effort and special facility for effecting the leakage reduction. For example, each technique noted above requires the assembly or application of additional elements to the power operated device, such as the power tool. These assembly or application techniques require additional costly and time-consuming efforts during assembly of the tool components. Further, in many instances, the tool must be designed, or redesigned, to accommodate the elements necessary to accomplish the reduction of leakage loss of the lubricant.
Consequently, notwithstanding the traditional techniques noted above, there still exists a need to find a relatively inexpensive and highly effective technique for eliminating the undesirable creepage of lubricant from a lubricant-containing compartment of a power device housing, along an interlock of the housing and hence to the exterior and interior areas of another compartment of the housing.